"3 million of Florida's 18.7 million residents are seniors, the densest concentration of elderly folk in the country," according to a recent Slate article.

Why is that the case? Well, according to the same article, Florida has "good weather, effective marketing, low taxes, and a herd mentality."

Once senior citizens began collecting Social Security, they had enough money to live independently during their retirement; this trend, practically unheard of in the beginning of the 20th century, became increasingly common during the rosy economy the U.S. had after World War II.

Around that time, according to the article, Florida was one of the least populous states in the nation, so real estatea developers bought up land and promoted the state as a great place to live, in part thanks to its warm climate.

But the growth had to level off at some point, and now many parts of Florida seem to have been built up to meet more demand than there actually is. And, of course, the law of supply and demand should always be on investors' minds.

Orlando, Miami and West Palm Beach came in third, fourth and fifth, respectively, on NuWire's list of the Top 5 Overbuilt U.S. Markets in 2007. And one Florida market is overloaded in another way: Jacksonville was third on NuWire's Top 10 Foreclosure Markets for 2007. These factors could contribute to investors being able to purchase properties below market value, but investors need to crunch the numbers before jumping into a deal just because the price is low.

In addition, investors interested in Florida should remember to pay some attention to the other age groups in the state. Florida is home to a lot of colleges and universities and thus has a large young adult population. Two cities in Florida--Tallahassee and Gainesville--were first and third, respectively, on NuWire's 2007 list of the Top 10 Small College Towns for Investment.